In recent years, a semiconductor device uses a multilayer wiring structure for achieving higher integration.
In order to increase the operating speed of the device in such a multilayer wiring structure, it is necessary to reduce parasitic capacitance between wires and delay resistance due to wiring resistance.
Therefore, there is a case where an interlayer insulating film with a low dielectric constant is provided.
As such an interlayer insulating film, there has been proposed a fluorocarbon (CFx) film having an extremely low relative dielectric constant (less than 3.0).
In this case, in a semiconductor device in which multiple circuit layers are formed on a semiconductor substrate formed with a number of semiconductor elements, each circuit layer is manufactured in the following manner.
First, a CFx film is formed on a lower-side circuit layer by plasma CVD and then a cap film made of, for example, SiCN (silicon carbonitride), SiC, SiN, or the like and a photoresist mask are laminated.
Then, using the photoresist mask, a hole (via hole) or a recess is formed in the cap film and the CFx film.
Then, after forming a barrier layer so as to cover an exposed surface including an inner surface of the recess, copper or the like as a main component of a wiring layer is embedded in the recess.
Finally, the excess copper and barrier layer (i.e. at a portion other than in the recess) are removed by CMP (Chemical Mechanical Polishing).
Herein, in the CMP, in order to prevent the CFx film from being directly subjected to a mechanical load, the CMP is stopped while the cap film remains (Patent Document 1).
However, SiCN (relative dielectric constant: about 5), SiC (relative dielectric constant: about 7), SiN (relative dielectric constant: about 8), or the like as the material of the cap film has a higher relative dielectric constant than CFx.
Therefore, if the cap film is provided, as the thickness of the interlayer insulating film decreases, the influence of the presence of the cap film having the high relative dielectric constant increases in the interlayer insulating film including the cap film. That is, the degree of the increase in relative dielectric constant due to the presence of the cap film becomes significant.
Consequently, there is a problem that even if the CFx film having a relative dielectric constant less than 3.0 is intentionally used as the interlayer insulating film, the advantage of the CFx film cannot be efficiently utilized due to the cap film.
In view of this, it has also been proposed to provide a wiring layer directly on a CFx film without providing such a cap film (Patent Document 2).